Electronically conductive polymer binder for lithium-ion battery electrode

ABSTRACT

A family of carboxylic acid groups containing fluorene/fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries. Triethyleneoxide side chains provide improved adhesion to materials such as, graphite, silicon, silicon alloy, tin, tin alloy. These binders enable the use of silicon as an electrode material as they significantly improve the cycle-ability of silicon by preventing electrode degradation over time. In particular, these polymers, which become conductive on first charge, bind to the silicon particles of the electrode, are flexible so as to better accommodate the expansion and contraction of the electrode during charge/discharge, and being conductive promote the flow battery current.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.13/294,885, filed Nov. 11, 2011, now U.S. Pat. No. 8,852,461, andentitled Electronically Conductive Polymer Binder for Lithium-IonBattery Electrode; which is a continuation of PCT Application No.PCT/US2010/035120, filed May 17, 2010 and entitled ElectronicallyConductive Polymer Binder for Lithium-Ion Battery Electrode; whichclaims priority to U.S. Provisional Application Ser. No. 61/179,258filed May 18, 2009, and U.S. Provisional Application Ser. No. 61/243,076filed Sep. 16, 2009, both entitled Electronically Conductive PolymerBinder for Lithium-ion Battery Electrode, Liu et al. inventors, each ofwhich applications is incorporated herein by reference as if fully setforth in their entirety.

STATEMENT OF GOVERNMENTAL SUPPORT

The invention described and claimed herein was made in part utilizingfunds supplied by the U.S. Department of Energy under Contract No.DE-AC02-05CH11231. The government has certain rights in this invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to lithium ion batteries, and morespecifically to an improved polymeric binder for forming siliconelectrodes resulting in battery electrodes of increased charge density.

2. Background of the Invention

Lithium-ion batteries are a type of rechargeable battery in whichlithium ions move between the negative and positive electrode. Thelithium ion moves through an electrolyte from the negative to thepositive during discharge, and in reverse, from the positive to thenegative, during recharge. Most commonly the negative electrode is madeof graphite, which material is particularly preferred due to itsstability during charge and discharge cycles as it forms solidelectrolyte interface (SEI) layers with very small volume change.

Lithium ion batteries and finding ever increasing acceptance as powersources for portable electronics such as mobile phones and laptopcomputers that require high energy density and long lifetime. Suchbatteries are also finding application as power sources for automobiles,where recharge cycle capability and energy density are key requirements.In this regard, research is being conducted in the area of improvedelectrolytes, and improved electrodes. High-capacity electrodes forlithium-ion batteries have yet to be developed in order to meet the40-mile plug-in hybrid electric vehicle energy density needs that arecurrently targeted.

One approach is to replace graphite as the negative electrode withsilicon. Notably graphite electrodes are rated at 372 mAh/g (milliamphours per gram) at LiC₆, while silicon electrodes are rated more thantenfold better at 4,200 mAh/g at Li_(4.4)Si. However, numerous issuesprevent this material from being used as a negative electrode materialin lithium-ion batteries. Full capacity cycling of Si results insignificant capacity fade due to a large volume change during Liinsertion (lithiation) and removal (de-lithiation). This volumetricchange during reasonable cycling rates induces significant amounts ofstress in micron size particles, causing the particles to fracture. Thusan electrode made with micron-size Si particles has to be cycled in alimited voltage range to minimize volume change.

Decreasing the particle size to nanometer scale can be an effectivemeans of accommodating the volume change. However, the repeated volumechange during cycling can also lead to repositioning of the particles inthe electrode matrix and result in particle dislocation from theconductive matrix. This dislocation of particles causes the rapid fadeof the electrode capacity during cycling, even though the Si particlesare not fractured. Novel nano-fabrication strategies have been used toaddress some of the issues seen in the Si electrode, with some degree ofsuccess. However, these processes incur significantly highermanufacturing costs, as some of the approaches are not compatible withcurrent Li ion manufacture technology. Thus, there remains the need fora simple, efficient and cost effective means for improving the stabilityand cycle-ability of silicon electrodes for use in Lithium ionbatteries.

SUMMARY OF INVENTION

By way of this invention, a new class of binder materials has beendesigned and synthesized to be used in the fabrication of siliconcontaining electrodes. These new binders, which become conductive onfirst charge, provide improved binding force to the Si surface to helpmaintain good electronic connectivity throughout the electrode, to thuspromote the flow of current through the electrode. The electrodes madewith these binders have significantly improved the cycling capability ofSi, due in part to their elasticity and ability to bind with the siliconparticles used in the fabrication of the electrode.

More particularly, we have found that a novel class of conductivepolymers can be used as conductive binders for the anode electrode.These polymers include poly 9,9-dioctylfluorene and 9-fluorenonecopolymer. The polyfluorene polymer can be reduced around 1.0 V (vs.lithium metal potential) and becomes very conductive from 0-1.0 V. Sincenegative electrodes (such as Si) operate within a 0-1.0 V window, thisallows polyfluorene to be used as an anode binder in the lithium ionbattery to provide both mechanical binding and electric pathways. As aunique feature of this polymer, by modifying the side chain of thepolyfluorene conductive polymer with functional groups such as —COOHthat will bond with Si nanocrystals, significantly improved adhesion canbe realized.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and others will be readily appreciated by theskilled artisan from the following description of illustrativeembodiments when read in conjunction with the accompanying drawings.

FIG. 1 depicts a generic chemical formula of a conductive polymer binderaccording to an embodiment of the present invention.

FIG. 2 is a plot of electrode capacity vs. cycle number for a Si anodemade with the conductive binder of FIG. 1 according to one embodiment ofthe invention, wherein R₁=R₂=(CH₂)₇CH₃, R₅=COOCH3, R₆=H and x=0.5, x′=0,y=0.175 and z=0.325.

FIG. 3 is a plot of Coulombic Efficiency (%) vs. Cycle Number for thesame Si anode/conductive binder electrode of FIG. 2.

FIG. 4 shows the voltage profile of the electrode of FIG. 2 in the firstseveral cycles of lithium insertion and removal.

FIG. 5 shows the de-lithiation performance of the same electrode atdifferent charge-rates.

FIG. 6 is a plot of Si electrode cycling behavior at fixed capacity forthe electrode of FIG. 2. When the lithiation is limited to a selectedcapacity, the de-lithiation capacities are stable in 100 cycles asshown.

FIG. 7 is a plot of cycling results for a PFFOMB(poly(9,9-dioctylfluorene-co-fluorenone-co-methylbenzoic acid)) binderused in combination with an electrolyte comprising LiPF₆ in EC/DEC+10%FEC.

FIG. 8 is the CV of the PFPFOFOMB polymer vs. Li/Li+.

FIG. 9 is a test of PFPFOFOMB (cross) vs. PFFOMB (triangle) polymers.

FIG. 10 is the cycling capacity of the Si/PFPFOFOMB electrode at C/10rate. (a) The electrode specific capacity based on Si weight. (b) Theelectrode area specific capacity.

FIG. 11 is the C/25 lithiation and variable delithiation rate of thecomposite electrode.

FIG. 12 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window. FIG. 12( a) illustrates electrodeperformance of Ant (5%):Si (95%) (0.31 mg/cm2) (Cycling rate: C/10).FIG. 12( b) illustrates electrode performance of Ant (10%):Si (90%)(0.42 mg/cm2) (Cycling rate: C/10). FIG. 12( c) illustrates FIG. 13 isFIG. 13 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window of Pyr (33%):Si (67%) (0.24 mg/cm2)(Cycling rate C/10).

FIG. 14 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window. FIG. 14( a) illustrates electrodeperformance of Ant0.7-co-TEG0.3 (33%):Si (67%) (0.34 mg/cm2) (Cyclingrate: C/10). FIG. 14( b) illustrates electrode performance ofAnt0.7-co-TEG0.3 (33%):Si (67%) (0.77 mg/cm2) (Cycling rate: C/10).

FIG. 15 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window. FIG. 15( a) illustrates electrodeperformance of Pyr0.7-co-TEG0.3(%):Si (95%)(0.11 mg/cm2) (C/10). FIG.15( b) illustrates electrode performance of Pyr0.7-co-TEG0.3 (33%):Si(67%)(0.22 mg/cm2) (C/10). FIG. 15( c) illustrates the electrodeappearance.

FIG. 16 illustrates the generic structures of the copolymer. FIG. 16( a)illustrates polymethacrylate backbone structure of the conductivepolymer binder. FIG. 16( b) illustrates polyacrylate ester backbonestructure of the conductive polymer binder. FIG. 16( c) illustratespolyvinylalcohol ether backbone structure of the conductive polymerbinder.

FIG. 17 illustrates electrode performance data for conductive polymerbinder with Si nanoparticles.

FIG. 18 illustrates electrode performance data for conductive polymerbinder with Si nanoparticles.

FIG. 19 illustrates electrode performance data for conductive polymerbinder with Si nanoparticles.

FIG. 20 illustrates electrode performance data for conductive polymerbinder with Si nanoparticles.

FIG. 21 illustrates electrode performance data for conductive polymerbinder with Si nanoparticles.

DETAILED DESCRIPTION

According to this invention the conductive polymers developed herein actas a binder for the silicon particles used for the construction of thenegative anode. They are mixed with the silicon nano sized siliconparties in a slurry process, then coated on a substrate such as copperor aluminum and thereafter allowed to dry to form the film electrode.Though the silicon particles can range from micron to nano size, the useof nano sized particles is preferred as such results in an electrodematerial that can better accommodate volume changes.

A fabrication method for the synthesis of one embodiment of the binderpolymer of this invention is as set forth below. First presented is ameans for preparing one of the monomers used in polymer formation, i.e.2,5-dibromo-1,4-benzenedicarboxylic acid, a reaction scheme forpreparing this monomer illustrated at paragraph [0020], immediatelybelow.

When the benzenedicarboxylic acid staring material has only one CH₃group, the reaction will end up with only one R═COOCH₃ group in thefinal product.

A. Synthesis of polymeric PFFO (poly(9,9-dioctylfluorene-co-fluorenone))

Exemplary of a method for forming one of the polymers of this inventionis provided with respect to one embodiment, according to the reactionscheme set forth at paragraph [0023], below. A mixture of9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester (0.83g, 1.5 mmol) commercially available from Sigma-Aldrich Company,2,7-dibromo-9-fluorenone (0.50 g, 1.5 mmol), (PPh₃)₄Pd(0) (0.085 g, 0.07mmol) and several drops of aliquat 336 in a mixture of 10 mL of THF(tetrahydrofuran) and 4.5 mL of 2 M Na₂CO₃ solution was refluxed withvigorous stiffing for 72 hours under an argon atmosphere. During thepolymerization, a brownish solid precipitated out of solution. The solidwas collected and purified by Soxhlet extraction with acetone as solventfor two days with a yield of 86%.

B. Synthesis of PFFOMB(poly(9,9-dioctylfluorene-co-fluorenone-co-methylbenzoic acid))

A mixture of 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol)ester (0.80 g, 1.43 mmol), 2,7-dibromo-9-fluorenone (0.24 g, 0.72 mmol),methyl 2,5-dibromobenzoate (0.21 g, 0.72 mmol), (PPh₃)₄Pd(0) (0.082 g,0.072 mmol) and several drops of Aliquat 336 in a mixture of 13 mL ofTHF(tetrahydrofuran) and 5 mL of 2 M Na₂CO₃ solution was refluxed withvigorous stirring for 72 h under an argon atmosphere. After reactionstopped, the solution was concentrated by vacuum evaporation and thepolymer was precipitated from methanol. The resulting polymer wasfurther purified by precipitating from methanol twice. The final polymerwas collected by suction filtration and dried under vacuum with a yieldof 87%.

C. Synthesis of PFFOBA(poly(9,9-dioctylfluorene-co-fluorenone-co-benzoic acid))

A mixture of PFFOMB (0.36 g) and KOH (2 g, 35 mmol) in 20 mL of THF and2 mL of H₂O was refluxed for 48 h under an argon atmosphere. Afterreaction stopped, the solution was concentrated by vacuum evaporationand polymer was precipitated from methanol. The resulting polymer wassuspended in 10 mL of concentrated H₂SO₄ with vigorous stiffing for 12hours. The final product was filtered, washed with water and dried witha yield of 96%.

Reaction scheme for forming conductive polymer with —COOCH₃ (PFFOMB) and—COOH(PFFOBA) groups on the side chains.

It has been found that the presence of —COOH groups serves to increasethe bindability of the polymer to the silicon particles of theelectrode. In particular, one can position carboxylic acid groups inconnection with the 9^(th) position of fluorene backbone. The belowformula depicts the general structure of this type of polymer.

Wherein x=0, x′ and y=>0, and z<=1, and x′+y+z=1, R₃ and R₄ can be(CH₂)_(n)COOH, n=0-8, and R₅ and R₆ can be any combination of H, COOHand COOCH₃.

Another variation is to adjust the number of COOH groups bycopolymerizing x monomer into the main chains as illustrated in theformula shown below. By adjusting the ratio of x:x′, the number of —COOHgroups can be controlled without changing the electronic properties ofthe conductive binders. Exemplary of such a composition is asillustrated below by the following formula.

Herein, x, x′, y>0, and z<=1, with x+x′+y+z=1. R₁ and R₂ can be(CH₂)_(n)CH₃, n=0-8. R₃ and R₄ can be (CH₂)_(n)COOH, n=0-8. R₅ and R₆can be any combination of H, COOH and COOCH₃; and the “x, x′” unit isfluorene with either alkyl or alkylcarboxylic acid at the 9,9′positions; the “y” unit is fluorenone, The H positions of the back boneof fluorenon and fluorene also can be substituted with functional groupssuch as COOH, F, Cl, Br, SO₃H, etc.

In still another embodiment, one can increase the flexibility of thepolymer by introducing a flexible section between repeating units. Thisis illustrated as shown below where a flexible chain section such asalkyl or polyethylene can be used to connect A sections together tofurther improve elasticity, the structure illustrated by the belowformula:

where n>=0, and the A sections are defined as follows:

Wherein0<=x, x′, y and z<=1 and x+x′+y+z=1.R₁ and R₂ can be (CH₂)_(n)CH₃, n=0-8, R₃ and R₄ can be (CH₂)_(n)COOH,n=0-8, R₅ and R₆ can be any combination of H, COOH and COOCH₃.

Most of the highly conjugated conductive polymers have rigid backbones,and the elasticity of the polymers is low. In order to accommodatevolume expansion incurred during the Li interacalation andde-intercalation in the alloys, it is important that the conductivepolymer binders have certain degree of elasticity. One method toincrease flexibility is to synthetically introduce flexible units (n)into the polymer system as show above. Unit n is a flexible alkyl orpolyethylene portion. This flexible unit (n) can be one or many of —CH₂units depending upon the requirements for a particular alloy system, orcould be other types of liner units depending on the ease of synthesis.Both x, x′, y and z units could be one or many fluorene or fluorenoneunits. One possible structure is of a random copolymer with a fewpercent of flexible units distributed along the fluorene main chain. TheR₁-R₆ units could be either one of the choices, and it is not necessarythey be all the same in a polymer chain. Increasing the length of theside chains may also have an effect on the flexibility of the polymerbinder. Therefore, the number of units in R₁-R₆ is also subject tochange during an optimization process. One may change the number ofunits of the R₁-R₆, and look for improved cell cycling performance asindication of optimization.

Another issue is the stability and impedance of the interface betweenthe active cathode material and electrolyte. The binder may cover (thatis, over-coat) all the active materials at higher binder loadings. Suchover-coverage will modify the interface stability and impedance. Varyingthe number of units in R₁-R₆ will play a significant role in optimizingthe charge transfer impedance at the interface.

Current polymer structures that have been synthesized and tested inlithium ion battery are shown as illustrated by the below.

PFFO (poly(9,9-dioctylfluorene-co-fluorenone))

PFFOMB (poly(9,9-dioctylfluorene-co-fluorenone-co-methylbenzoic acid))

PFFOBA (poly(9,9-dioctylfluorene-co-fluorenone-co-benzoic acid))

Once the conductive polymers have been synthesized they can be mixedwith the silicon particles, and coated onto a substrate such as copperand allowed to dry to form the electrode material. A more detaileddiscussion of electrode preparation is presented below. An advantage ofthe use of these conductive polymers of the present invention is thatthey are easily compatible with current slurry processes for makingelectrodes, thus requiring no special steps or equipment.

Process for Making Slurry of Conductive Polymer

Si/conductive polymer mixtures were made by dissolving 0.09 g of theconductive polymer of FIG. 1 (i.e., PFFOBA, wherein R₁═R₂═(CH₂)₇CH₃,R₅═COOCH₃, R₆═H, and x=0.5, x′=0, y=0.175 and z=0.325)) in 2.6 g ofchlorobenzene. 0.18 g of Si was dispersed in the polymer solution tomeet the desired Si: polymer ratios at 2:1. To ensure the thoroughmixing of the Si nanoparticles into the polymer solution, a Branson 450sonicator equipped with a solid horn was used. The sonication power wasset at 70%. A continuous sequence of 10 second pulses followed by 30second rests was used. The sonic dispersion process took about 30 min.All of the mixing processes were performed in Ar-filled glove boxes.

Process for Making Conductive Glue of AB/PVDF

By way of comparison to the conductive polymers of this invention,illustrated in FIGS. 2 and 3, slurries of AB: PVDF (acetyleneblack/polyvinylidene fluoride) at 0.2:1 ratios by weight were made bydissolving 5 g of PVDF in to 95 g of NMP to make a 5% PVDF in NMPsolution. Proper amounts of AB was dispersed in the PVDF solution tomeet the desired AB: PVDF ratios. To ensure the thorough mixing of theAB nanoparticles into the PVDF solution, the Branson 450 sonicatorequipped with a solid horn was used. The sonication power was set at70%. A continuous sequence of 10 s pulses followed by 30 s rests wasused. The sonic dispersion process took ca. 30 min. All of the mixingprocesses were performed in Ar-filled glove boxes.

Process for Making Slurry of Si/AB/PVDF

0.86 g Si was mixed with 7.16 g of the conductive glue (PVDF:AB=1:0.2 byweight in 95% PVDF NMP solution). To ensure the thorough mixing of theSi nanoparticles into the glue solution, the Branson 450 sonicatorequipped with a solid horn was used. The sonication power was set at70%. A continuous sequence of 10 s pulses followed by 30 s rests wasused. The sonic dispersion process took about 30 min. All of the mixingprocesses were performed in Ar-filled glove boxes.

Process for Making the Electrode

All electrode laminates were cast onto a 20 μm thick battery-grade Cusheet using a Mitutoyo doctor blade and a Yoshimitsu Seiki vacuumdrawdown coater to roughly the same loading per unit area of activematerial. The films and laminates were first dried under infrared lampsfor 1 h until most of the solvent was evaporated and they appeareddried. The films and laminates were further dried at 120° C. under 10⁻²Torr dynamic vacuum for 24 h. The film and laminate thicknesses weremeasured with a Mitutoyo micrometer with an accuracy of ±1 μm. Thetypical thickness of film is about 20 μm. The electrodes were compressedto 35% porosity before coin cell assembly using a calender machine fromInternational Rolling Mill equipped with a continuously adjustable gap.

Process for Fabricating Coin Cell

Coin cell assembly was performed using standard 2325 coin cell hardware.A 1.47 cm diameter disk was punched out from the laminate for use in thecoin cell assembly as a working electrode. Lithium foil was used inmaking the counter electrode. The counter electrodes were cut to 1.5 cmdiameter disks. The working electrode was placed in the center of theouter shell of the coin cell assembly and two drops of 1 M LiPF₆ inEC:DEC (1:1 weight ratio) electrolyte purchased from Ferro Inc. wereadded to wet the electrode. A 2 cm diameter of Celgard 2400 porouspolyethylene separator was placed on top of the working electrode. Threemore drops of the electrolyte were added to the separator. The counterelectrode was placed on the top of the separator. Special care was takento align the counter electrode symmetrically above the workingelectrode. A stainless steel spacer and a Belleville spring were placedon top of the counter electrode. A plastic grommet was placed on top ofthe outer edge of the electrode assembly and crimp closed with acustom-built crimping machine manufactured by National Research Councilof Canada. The entire cell fabrication procedure was done in anAr-atmosphere glove box.

Process for Testing Coin Cell

The coin cell performance was evaluated in a thermal chamber at 30° C.with a Maccor Series 4000 Battery Test System. The cycling voltagelimits were set at 1.0 V at the top of the charge and 0.01 V at the endof the discharge.

Chemicals

All the starting chemical materials for synthesis of the conductivepolymer were purchased from Sigma-Aldrich. Battery-grade AB with anaverage particle size of 40 nm, a specific surface area of 60.4 m²/g,and a material density of 1.95 g/cm³ was acquired from Denka SingaporePrivate Ltd. PVDF KF1100 binder with a material density of 1.78 g/cm³was supplied by Kureha, Japan. Anhydrous N-methylpyrrolidone NMP with 50ppm of water content was purchased from Aldrich Chemical Co.

As described above, the conductive polymers of this invention can beused as electrically conductive binders for Si nanoparticles electrodes.The electron withdrawing units lowering the LUMO level of the conductivepolymer make it prone to reduction around 1 V against a lithiumreference, and the carboxylic acid groups provide covalent bonding withOH groups on the Si surface by forming ester bonds. The alkyls in themain chain provide flexibility for the binder.

Results of the various tests that were conducted are as reported in thevarious plots of FIGS. 2-6. FIG. 2 shows the new conductive polymerbinder in combination with Si nanoparticles much improving the capacityretention compared to conventional acetylene black (AB) andpolyvinylidene difluride (PVDF) conductive additive and binder as acontrol. FIG. 3 illustrates the improved coulombic efficiency of theconductive binder/Si electrode of the invention compared with theconventional AB/PVDF approach. FIG. 4 illustrates results showing verysimilar voltage profiles of the conductive polymer/Si electrode to thepure Si film type of electrode. FIG. 5 plots the rate performance of theconductive polymer/Si electrode of the invention, showing good results.Evan at a 10 C rate, there is still more than half of the capacityretention. Finally, FIG. 6 illustrates cycleability of the siliconelectrode made with the copolymer binder of the invention, which is verygood at limited capacity range. There is no capacity fade in 100 cyclesat 1200 mAh/g and 600 mAh/g fixed capacity cycling. FIG. 7 illustratescycling results for a PFFOMB binder using an electrolyte comprising 1.2M LiPF6 in EC/DEC (ethylene carbonate and diethylene carbonate) plus 10%FEC (fluoroethylene carbonate or fluorinated ethylene carbonate), theFEC additive serving as a stabilizer.

C. Synthesis of PFPFOFOMB(poly(2,7-9,9-dioctylfluorene-co-2,7-9,9-(di(oxy-2,5,8-trioxadecane))fluorine-co-2,7-fluorenone-co-2,5-1-methylbenzoicester)) (an analog of PFFOMB) binder and the Si electrode performance

Triethyleneoxide side chains provide improved adhesion to materials suchas, graphite, silicon, silicon alloy, tin, tin alloy. Additionallytriethyleneoxide side chains provide a higher swelling rate thatimproves ionic conduction. In one embodiment, a 30% weight increaseabove dry weight provides an increase in ionic conduction while alsoavoiding bursting of the battery.

Scheme 1 lists the synthetic process to form the tosylatedtriethyleneoxide methylether.

The number of ethyleneoxide units can vary from 0 to 10000 (n=0-10000),and n can be an exact number or an average. The higher number of n iscalled an oligoethyleneoxide monomethylether. Scheme 2 gives the genericstructure of a possible family of the tosylate products. The typicalnumber of n is from 1-5.

Scheme 3 is the schematic process of synthesis of the PFO monomer usingtosylated triethlyeneoxide monomethylether. Tosylate with otheroligothyleneoxide monomethylether as in Scheme 2 can also be used toform different lengths of ethyleneoxide chains at the 9 positions of thefluorene.

The PFO monomer can be incorporated into the PFFOMB polymer binder(IB-2643) in the process described in Scheme 4. Both PFPFOFOMB andPFPFOFOBA are random copolymers, where all the units are locatedrandomly. The subscribed numbers in the polymer molecular structureindicates the ratios among all the units. This synthesis processrequires to have a=b+c+d. The composition we used to generate thepolymer PFPFOFOMA is a=3, b=1, c=1 and d=1, so the ratio between theOctylfluorene (segment a) and triethyleneoxide fluorene (segment b) is3/1. The segment b has higher polarity due to the triethyleneoxidechains therefore increases electrolyte uptake and improved adhesionbetween the particle surfaces and the binder. With synthetic Scheme 4,a, b, c, and d can vary from 0-1000 as long as the condition of a=b+c+dis satisfied.

Scheme 5 is an alternative synthesis process to make both PFPFOFOMB andPFPFOFOBA polymers. This alternative process does not have theconstraint as the process described in Scheme 4. Therefore, a, b, c, dcan be another number between 0-1000. The alternation of the numbers hasa major impact of the binder when combined with silicon.

The above binder is combined with Si (Sn or other alloy of the kind)particles to formulate a lithium ion negative electrode. The particlecan be spherical, a wire, or a plate. For spherical or pseudo sphericalparticles, the diameter can be from 0.1 nm-100 micron. For wires, thespherical cross-section is in 0.1 nm-100 micron. The length is 1 nm-1000micron. For a plate, the thickness is in 0.1 nm-100 micron. The plainsize is also 0.1 nm-100 micron. The binder and particle compositescontain at least one particle.

The polymer synthesized is demonstrated in Schematic 6. This polymer iscombined with Si nanoparticles. The Si nanoparticles have an averageparticle size of 50-70 nm diameter. This Si sample is purchased fromNanostructured & Amorphous Materials Inc. The composition of theelectrode laminate is 34% by weight of PFPFOFOMB polymer, and 66% Sinanoparticles. The electrode is cast by a slurry process describedbelow.

Monomer Synthesis

10-Tosyloxy-2,5,8-trioxadecane Triethlyene glycol monomethylether (10 g,61 mmol) was dissolved in THF (50 mL) and cooled to 0° C. in an icebath. A solution of KOH (5.6 g, 100 mmol) in 10 mL water was slowlyadded to the mixture, and then a solution of TsCl (9.5 g, 50 mmol) in 20mL THF was added drop-wise over 20 min. with vigorous stiffing. Afterstiffing overnight in an ice bath, the mixture was poured into distilledwater (200 mL) and extracted with CH₂Cl₂ (2×100 mL). The combinedorganic solutions were washed with saturated NaHCO₃ solution (2×100 mL),distilled water (2×100 mL), dried over MgSO₄, and concentrated underreduced pressure to give 15.7 g as a clear colorless oil in 99% yield.¹H NMR (300 MHz, CDCl₃) δ 2.3 (s, 3H), 3.22 (s, 3H), 3.28-3.70 (m, 10H),4.04 (t, 2H), 7.24 (d, 2H), 7.68 (d, 2H).

2,7-Dibromo-9,9(di(oxy-2,5,8-trioxadecane))fluorine 2,7-dibromofluorene(5.0 g, 15.4 mmol) was dissolved in dried THF solution (30 mL). Sodiumhydride (1.0 g, 40 mmol) was added to the THF solution at roomtemperature and refluxed for 5 hours. 10-Tosyloxy-2,5,8-trioxadecane(11.8 g, 37 mmol) in 20 mL of dry THF was added dropwise to the refluxedsolution. The mixture was allowed to refluxed over night, then cooleddown, poured into distill water and extracted with chloroform (2×100mL). The combined organic solutions were washed with saturated NaClsolution (2×100 mL), distilled water (1×100 mL), dried over MgSO₄, andconcentrated under reduced pressure. Crude oil was further purified bycolumn chromatography using hexane/ethyl acetate (50/50) as eluant. TLC(ethyl acetate/Hexane=1/1) R_(f)=0.12. The fraction at R_(f)=0.12 wascollected and concentrated to give 5.7 product in 60% yield. ¹H NMR (300MHz, CDCl₃) δ 2.34 (t, 4H), 2.77 (t, 4H), 3.10-3.60 (m, 22H), 7.40-7.60(m, 6H).

Polymerization

Poly(2,7-9,9-dioctylfluorene-co-2,7-9,9-(di(oxy-2,5,8-trioxadecane))fluorine-co-2,7-fluorenone-co-2,5-1-methylbenzoicester): A mixture of 9,9-dioctylfluorene-2,7-diboronic acidbis(1,3-propanediol) ester (1.10 g, 1.97 mmol),9,9-(di(oxy-2,5,8-trioxadecane))fluorine (0.44 g, 0.71 mmol)2,7-dibromo-9-fluorenone (0.24 g, 0.72 mmol), methyl2,5-dibromobenzoate(0.21 g, 0.72 mmol), (PPh₃)₄Pd(0) (0.082 g, 0.072 mmol) and severaldrops of Aliquat 336 in a mixture of 13 mL of THF and 5 mL of 2 M Na₂CO₃solution was refluxed with vigorous stirring for 72 h under an argonatmosphere. After reaction stopped, the solution was concentrated byvacuum evaporation and the polymer was precipitated from methanol. Theresulting polymer was further purified by precipitating from methanoltwice.

PFPFOFOMB and Electrode Characterization

Circular voltamegram (CV) of PFPFOMB was measured against a Lireference. The Polymer was coated on Cu current collector. Electrolyteis 1M LiPF₆ in EC/EMC/DMC 1/1/1 with 10% FEC electrolyte. The conditionsfor CV are polymer weight 70 microgram, voltage step 0.2 mV/s, area 1.6cm2.

FIG. 8 is the CV of the PFPFOFOMB polymer vs. Li/Li+. The swelling rateof this PFPFOFOMB polymer was also measured against the 1M LiPF6, EC/DEC(1:1, wt) electrolyte, and compared with the PFFOMB polymers. The filmthickness is controlled around 10 micron. PFPFOFOMB polymer has muchhigher swelling in the electrolyte compared to the PFFOMB polymer.

FIG. 9 is a test of PFPFOFOMB (cross) vs. PFFOMB (triangle) polymers.The polymer binder solution was made by dissolving 90 mg of polymerbinder in 2.6 mL of N-methylpyrrolidone (NMP) solution with magneticstiffing. 180 mg of the Si nano powder was added into the bindersolution and sonicated for 2 minutes to make uniformed slurry. Theslurry was coated on a piece of Cu current collector with a doctor bladeat a gap of 25 μm. All the processes were done in the inert atmosphereglove box. The laminate was vacuum dried at 120° C. over night. Thelaminate thickness 12 μm. The electrode was pouch out with a 9/16″pouch. The weight of active materials Si is 0.28 mg. The electrode wasassembled into a coin cell with Li metal counter electrode, Celgard®2500 separator and 1M LiPF₆ in EC/EMC/DMC 1/1/1 with 10% FECelectrolyte. FIG. 1 shows the coin cell cycling test in 30° C.temperature oven at C/10 current (0.12 mA) between 0.01V-1V voltagerange. The C-rate calculation of the Si based electrode is assuming theSi has the theoretical capacity of 4200 mAh/g.

FIG. 10 is the cycling capacity of the Si/PFPFOFOMB electrode at C/10rate. (a) The electrode specific capacity based on Si weight. (b) Theelectrode area specific capacity. The C-rate performance of theSi/PFPFOFOMB composite electrode was also tested in 1 M LiPF6 EC/DEC(3:7 weight) 30% FEC and reported in FIG. 11.

FIG. 11 is the C/25 lithiation and variable delithiation rate of thecomposite electrode. The PFPFOFOMB polymer based Si electrode has muchimproved performance and can deliver the full theoretical capacity ofthe Si particle (˜3500 mAh/g) with good rate retention. The adhesion ofPFPFOFOMB/Si is much stronger than that of the PFFOMB/Si based system.Adhesion and swelling are keys for the improve performance of thePFPFOFOMB conductive polymer over PFFOMB polymer.

Further embodiments of this invention enable three aspects ofimprovement to the binders described above, 1) low cost startingmaterials and a low cost manufacturing process, 2) adjustable electronicproperties without complicated material design and manufacture, and 3)adjustable adhesion and electrolyte swelling without complicatedmaterial design and manufacture.

Various embodiments also provide a low cost way to achieve betterperformance of the electrode binder in lithium ion batteries especiallyfor Si, Sn, or graphite and alloy based volume changing lithium storagematerials.

Various embodiments also describe new material for design and synthesisof the conductive binder. For example, the binders described below areside chain electronic conducting rather than main chain conducting asdescribed above.

Attempts to find electronic and low cost binders has led us to theutilization of the comb branch type of polymer with a non-conductivepolymethacrylate backbone and conjugated side chained polymer system.Two types of conductive moiety anthracene and pyrene have beencharacterized as shown below: (a) anthracene; (b) pyrene.

The functionalized anthracene and pyrene can be purchased from AldrichChemical company. Below illustrates the functionalized chemicals withhydroxide groups from Aldrich: (a) unctionalized anthracene and (b)functionalized pyrene.

A methacrylate functional group can be connected to the hydroxyl groupof the anthracene or pyrene as shown in the reaction Scheme 1 and 2.These methacrylate functional groups can go through a polymerizationprocess to generate polymers.

One embodiment of the invention is to use the methacrylate anthracenemonomer made in Scheme 1 reaction to polymerize into methacrylatepolymers as shown in Scheme 3. The side chains are anthracene units. Thestacking of the anthracene units provides electronic conduction in thispolymer. This conductive polymer is side chain electronic conducting.The polymer in Scheme 3 is referred to as PMAN.

The PMAN polymer can be partially hydrolized to contain carboxylic acidgroups in the polymer side chain according to Scheme 4. Depending on theconditions of the hydrolysis, the ratio between a/b can varysignificantly. A longer hydrolysis time will lead to lower ratio ofanthracene and higher ratio of carboxylic acid. These acid groups willprovide additional bonding with a Si particle surface to improveadhesion between the binder and the Si particles. Alternatively, theacid groups can be introduced during the polymerization process as inScheme 5. The feeding ratio between the two monomers determines the a/bratio. In both cases, the final polymers are random copolymers.

To further adjust the adhesion and electrolyte intake properties, ashort oligoethyleneoxide monomethylether chain can be copolymerized intothe polymer structure as shown in Scheme 6. The final polymer is arandom copolymer of the anthracene and oligoethyleneoxidemonomethylether branches. The ratio of a/b in the PMANEO polymer isdetermined by the reactant ratio.

Carboxylic acid groups can also be incorporated into the PMANEO polymerin two different methods. The hydrolysis method is shown in Scheme 7,and the copolymerization of monomers with carboxylic acid group as inScheme 8. Both PMANEOACs are a random copolymer structures.

Scheme 9 shows the generic structure of the copolymers. The R₁, R₂ andR₃ are randomly distributed, and the ratio of a/b/c reflect the relativeabundance of the side chain unit. The R₁ can be either one of a type ofstructure among the naphthalene to fluorene or a mixture of thestructures. The R₂ is the oligoethyleneoxide monomethylether and thevariable m can range from 0 to 1000, and can be exact or an average. Thepreferred range of values of m are from 0 to 3. The R₃ is a hydrogen (H)to make the c structure carboxylic acid units.

The function of R₁ side chains is to make the polymer conductive basedon a side chain stacking arrangement. The mixing of the R₁ possiblestructures from naphthalene to fluorene can fine tune the band gap ofthe overall polymer to improve the doping properties and electronicconducting capabilities.

The R₂ units are used to adjust both the ability for the polymers toswell when exposed to an electrolyte. The high polarity of theethyleneoxides can also provide adhesion between the particles and thepolymer itself.

The R₃ units are carboxylic acid groups. They are used to form esterchemical bonding to the Si₂O surface on Si particle. This chemicalbonding significantly improves the adhesion between the particles andthe binder.

One embodiment includes the synthesis of the conductive polymersincluding R₁ and R₂ with the third polymer c=0, so R₃ is not included inthe copolymer based on the Scheme 9 generic structure.

Referring to Table 1 below, both the Anthracene/ethyleneoxide (EO)copolymers and pyrene/EO copolymer compositions are illustrated byweight.

TABLE 1 Anthracene Triethyleneoxide (R1) Triethyleneoxide (R2) Pyrene(R1) (R2) 100% 0% 100% 0% 90% 10% 90% 10% 70% 30% 70% 30% 50% 50% 50%50%

The electrode composition and structure with Si and conductive polymerare designed around the specification below.

-   -   1. Si materials 50-70 nm Si nanoparticles    -   2. Polymer to Si weight composition is 33% and 67%.    -   3. Electrode thickness: ˜10 micron    -   4. Area loading: ˜1 mAh/cm2

Examples of the polymers synthesized, electrode compositions and cyclingresults. Polymer structure is R1 is anthracene, b=0 and c=0 based onScheme 9.

TABLE 2 Electrode composition and performance summary. See also FIG. 12.Polymer/Si 1^(st) Charging weight Mass Loading (Si (mAh/g, ratioLoading) (mg/cm2) mAh/cm2) 1^(st) CE 5^(st) CE Ant (5%):Si 0.31 ± 0.0413150 ± 277, 0.91 0.74 0.98 (95%) (0.29 ± 0.041) Ant (10%):Si 0.42 ±0.038 2380 ± 147, 0.91 0.73 0.97 (90%) (0.38 ± 0.038) Ant (10%):Si 0.037(0.034) 4500, 0.24 0.71 (90%)

FIG. 12 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window. FIG. 12( a) illustrates electrodeperformance of Ant (5%):Si (95%) (0.31 mg/cm2) (Cycling rate: C/10).FIG. 12( b) illustrates electrode performance of Ant (10:Si (90%) (0.42mg/cm2) (Cycling rate: C/10). FIG. 12( c) illustrates electrodeperformance of Ant (10%):Si (90%) (0.037 mg/cm2) (Cycling rate: C/10).

TABLE 3 Electrode composition and performance summary. Polymer structureis R1 is Pyrene, b = 0 and c = 0 based on Scheme 9. See also FIG. 13.1^(st) Charging Polymer/Si Mass Loading (Si (mAh/g, weight ratioLoading) (mg/cm2) mAh/cm2) 1^(st) CE 3^(rd) CE Pyr (33%):Si 0.24 ± 0.0342730 ± 357, 0.44 0.68 0.95 (67%) (0.16 ± 0.034)

FIG. 13 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window of Pyr (33%):Si (67%) (0.24 mg/cm2)(Cycling rate C/10).

TABLE 3 Electrode composition and performance summary. Polymer structureis R1 is anthracene and R2 is triethyleneglycol monomethylether, c = 0based on Scheme 9. See also FIG. 14. a:b weigh ratio is 7:3 Mass Loading1^(st) Charging Si is 67% of the (Si Loading) (mAh/g, 1^(st) 2^(nd)electrode weight (mg/cm2) mAh/cm2) CE CE Ant0.7-co-TEG0.3 0.34 ± 0.0342930 ± 273, 0.66 0.74 0.96 (33%):Si (67%) (0.23 ± 0.034)Ant0.7-co-TEG0.3 0.77 ± 0.036 3100 ± 133, 1.6  0.71 0.94 (33%):Si (67%)(0.52 ± 0.036)

FIG. 14 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window. FIG. 14( a) illustrates electrodeperformance of Ant0.7-co-TEG0.3 (33%):Si (67%) (0.34 mg/cm2) (Cyclingrate: C/10). FIG. 14( b) illustrates electrode performance ofAnt0.7-co-TEG0.3 (33%):Si (67%) (0.77 mg/cm2) (Cycling rate: C/10).

TABLE 4 Electrode composition and performance summary. Polymer structureis R1 is pyrene and R2 is triethyleneglycol monomethylether, c = 0 basedon Scheme 9. See also FIG. 15. Mass Loading 1^(st) Charging (Si Loading)(mAh/g, 1^(st) 4^(th) a:b weigh ratio is 7:3 (mg/cm2) mAh/cm2) CE CEPyr0.7-co-TEG0.3 (5% 0.11 ± 0.036 4670 ± 973, 0.69 0.96 by weight):Si(95% by (0.11 ± 0.036) 0.50 weight) Pyr0.7-co-TEG0.3 0.22 ± 0.034 3370 ±478, 0.71 0.96 (33%):Si (67%) (0.15 ± 0.034) 0.51

FIG. 15 illustrates electrode performance based on cycling at C/10 rateat 1V to 0.01 V voltage window. FIG. 15( a) illustrates electrodeperformance of Pyr0.7-co-TEG0.3(%):Si (95%)(0.11 mg/cm2) (C/10). FIG.15( b) illustrates electrode performance of Pyr0.7-co-TEG0.3 (33%):Si(67%)(0.22 mg/cm2) (C/10). FIG. 15( c) illustrates the electrodeappearance.

Planned synthesis of R₁=pyrene, b=0, R₃=H, Na or Li. a/c ratio variousfor the Si and Si based alloy materials. There are two routes forsynthesis of this class of polymer, based on Scheme 4 or 5 usingmethacrylate pyrene monomer. The polymer is later converted into Na orLi salts by neutralizing in NaOH or LiOH solution. This bind will beused to combine with 3M Si alloy based anode materials.

General Electrode Compositions

The electrode is a composite of at least one active material particleand conductive polymer binder.

The active material particles can be Si micron or nano particles, or canbe Sn micron or nano particles; or can be any alloy that contain Si, Sn,or graphite and other elements.

The active material particles can also be graphite particles mixed withthe above mentioned Si and Sn materials in different compositions.

This invention has been described herein in considerable detail toprovide those skilled in the art with information relevant to apply thenovel principles and to construct and use such specialized components asare required. However, it is to be understood that the invention can becarried out by different equipment, materials and devices, and thatvarious modifications, both as to the equipment and operatingprocedures, can be accomplished without departing from the scope of theinvention itself.

Possible Backbone Structures of the Conductive Polymer Binder

Polymethacrylate Ester

Polyacrylate Ester

Polyvinylalcohol ether (if the connection between R and the backbone isoxygen

-   -   n can be from 1 to 10 million    -   a, b, c are the ratios between the numbers of R₁, R₂ and R₃        groups.    -   a+b+c=1; where the possible number of a=0−1, the possible number        of b=0−1 and the possible number of c=0−1.

Possible R₁ Structures

A=(CH₂)_(a), a=0-100

R₁ can be pure or the mixtures any of the above structures.

Oxygen also can be all or partially replaced with NH, or NCH₃

The end oxygen or/and nitrogen are connected with the polymer backbones.

Possible R₂ Structures

R₂═(OCH₂CH₂)_(m)CH₃ m=0-1000

-   -   The end oxygen is connected with the polymer backbones. R₂ can        be a mixture of the different length or oligoethyleneoxide        methylether.

Possible R₃ Structures

-   -   R₃ can be pure or mixtures of any of the above structures. The        end oxygen or/and nitrogen are connected with the polymer        backbone.

Typical Synthetic Procedures for the Conductive Polymer Binders

Synthesis of 9-anthrylmethyl methacrylate

9-Anthracenemethanol (30 g) was dissolved in freshly distilled THF (150mL). To the solution triethylamine (30 mL) and pyridine (20 mL) wereadded and the mixture was cooled down to 0° C. Then methacryloylchloride (21 mL) was added dropwise. After the addition, ice-water bathwas removed and the mixture was stirred for 1 hour. After water (75 mL)was added to the reaction flask, the solution was transferred intoseparatory funnel and extracted with diethyl ether (500 mL). The extractwas washed with aqueous HCl (1 M, 150 mL), aqueous NaHCO₃ (5%, 150 mL),and brine (150 mL), respectively. The solvent was evaporated in vacuumand recrystallized with methanol. (Product: 21 g) ¹H NMR (500 MHz,CDCl₃): δ 8.55 (s, 1H), 8.41 (d, J=8.9 Hz, 2H), 8.07 (d, J=8.4 Hz, 2H),7.61 (t, J=7.7 Hz, 2H), 7.53 (t, J=7.9 Hz, 2H), 6.25 (s, 2H), 6.08 (s,1H), 5.54 (s, 1H), 1.95 (s, 3H) ppm.

Synthesis of 1-pyrenemethyl methacrylate

The same procedure as that of 9-anthrylmethyl methacrylate was executed.1-pyrenemethanol (30 g), freshly distilled THF (280 mL), triethylamine(28 mL), pyridine (18 mL), methacryloyl chloride (19 mL) was used.(Product: 43 g) ¹H NMR (500 MHz, CDCl₃): δ 8.35 (d, J=9.2 Hz, 1H), 8.25(t, J=6.6 Hz, 2H), 8.21 (d, J=9.8 Hz, 2H), 8.12 (t, J=4.6 Hz, 3H), 8.06(m, 1H), 6.18 (s, 1H), 5.95 (s, 2H), 5.59 (s, 1H), 2.00 (s, 3H) ppm.

Synthesis of poly(9-anthrylmethyl methacrylate)

9-Anthrylmethyl methacrylate (1.2 g) was dissolved in freshly distilledTHF (4 mL). To the solution 2,2′-azobis(2-methylpropionitrile) (AIBN) (8mg) was added. The mixture was degassed by three freeze-evacuate-thawcycles and heated to 60° C. for 24 hours. The product was purified byprecipitation with diethyl ether. (Product: 0.70 g) ¹H NMR (500 MHz,CDCl₃): δ 7.84 (br), 7.12 (br), 5.64 (br), 0.63 (br) ppm. GPC(CHCl₃,poly(styrene) standards, M_(n)=17000, PDI=2.2)

Synthesis of poly(1-pyrenemethyl methacrylate)

1-Pyrenemethyl methacrylate (1.2 g) was dissolved in freshly distilledTHF (4 mL). To the solution 2,2′-azobis(2-methylpropionitrile) (AIBN) (8mg) was added. The mixture was degassed by three freeze-evacuate-thawcycles and heated to 60° C. for 24 hours. The product was purified byprecipitation with diethyl ether. (Product: 1.1 g) ¹H NMR (500 MHz,CDCl₃): δ 7.48 (br), 5.09 (br), 1.80 (br), 0.71 (br) ppm. GPC(CHCl₃,poly(styrene) standards, M_(n)=21000, PDI=2.5)

Synthesis of poly(9-anthrylmethyl methacrylate-co-triethylene glycolmethyl ether methacrylate)

9-Anthrylmethyl methacrylate (5.0 g) and triethylene glycol methyl ethermethacrylate (1.8 g) were dissolved in freshly distilled THF (15 mL). Tothe solution 2,2′-azobis(2-methylpropionitrile) (AIBN) (20 mg) wasadded. The mixture was degassed by three freeze-evacuate-thaw cycles andheated to 60° C. for 24 hours. The product was purified by precipitationwith diethyl ether. (Product: 3.2 g) ¹H NMR (500 MHz, CDCl₃): δ 8.20(br), 7.84 (br), 7.28 (br), 5.85 (br), 3.42 (br), 1.56 (br), 0.75 (br)ppm. GPC(CHCl₃, poly(styrene) standards, M_(n)=19000, PDI=2.3)

Synthesis of poly(1-pyrenemethyl methacrylate-co-triethylene glycolmethyl ether methacrylate)

1-Pyrenemethyl methacrylate (5.0 g) and triethylene glycol methyl ethermethacrylate (1.7 g) were dissolved in freshly distilled THF (15 mL). Tothe solution 2,2′-azobis(2-methylpropionitrile) (AIBN) (20 mg) wasadded. The mixture was degassed by three freeze-evacuate-thaw cycles andheated to 60° C. for 24 hours. The product was purified by precipitationwith diethyl ether. (Product: 4.0 g) ¹H NMR (500 MHz, CDCl₃): δ 7.71(br), 5.37 (br), 3.96 (br), 3.26 (br), 1.83 (br), 0.79 (br) ppm.GPC(CHCl₃, poly(styrene) standards, M_(n)=34000, PDI=2.9)

Synthesis of poly(9-anthrylmethyl methacrylate-co-methacrylic acid)

9-Anthrylmethyl methacrylate (5.0 g) and methacylic acid (0.54 g) weredissolved in freshly distilled THF (10 mL). To the solution2,2′-azobis(2-methylpropionitrile) (AIBN) (20 mg) was added. The mixturewas degassed by three freeze-evacuate-thaw cycles and heated to 60° C.for 24 hours. The product was purified by precipitation with diethylether. (Product: 4.6 g)

Synthesis of poly(1-pyrenemethyl methacrylate-co-methacrylic acid)

1-pyrenemethyl methacrylate (5.0 g) and methacylic acid (0.50 g) weredissolved in freshly distilled THF (20 mL). To the solution2,2′-azobis(2-methylpropionitrile) (AIBN) (20 mg) was added. The mixturewas degassed by three freeze-evacuate-thaw cycles and heated to 60° C.for 24 hours. The product was purified by precipitation with diethylether. (Product: 4.1 g) ¹H NMR (500 MHz, DMSO-d₆): δ 12.7 (br), 7.68(br), 5.48 (br), 1.06 (br) ppm.

Electrode Performance Data for Some of the Conductive Polymer Binderwith the Si Nanoparticles

FIG. 17 shows electrode performance data for conductive polymer binder:

with Si nanoparticles. The electrode composition is polymer binder at33% by weight, and Si nanoparticles at 67%. The electrode is in a coincell with Li metal counter electrode. The cell is cycled between 0.01-1V at C/10 rate.

FIG. 18 shows electrode performance data for conductive polymer binder:

with Si nanoparticles. The electrode composition is polymer binder at33% by weight, and Si nanoparticles at 67%. The electrode is in a coincell with Li metal counter electrode. The cell is cycled between 0.01-1V at C/10 rate.

FIG. 19 shows electrode performance data for conductive polymer binder:

with Si nanoparticles. m/n ratio is 7/3. The electrode composition ispolymer binder at 33% by weight, and Si nanoparticles at 67%. Theelectrode is in a coin cell with Li metal counter electrode. The cell iscycled between 0.01-1 V at C/10 rate.

FIG. 20 shows electrode performance data for conductive polymer binder:

with Si nanoparticles. m/n ratio is 7/3. The electrode composition ispolymer binder at 33% by weight, and Si nanoparticles at 67%. Theelectrode is in a coin cell with Li metal counter electrode. The cell iscycled between 0.01-1 V at C/10 rate.

FIG. 21 shows electrode performance data for conductive polymer binder:

with Si nanoparticles. m/n ratio is 7/3. The electrode composition ispolymer binder at 33% by weight, and Si nanoparticles at 67%. Theelectrode is in a coin cell with Li metal counter electrode. The cell iscycled between 0.01-1 V at C/10 rate.

What we claim is:
 1. A polymeric composition with repeating units of theformula:

wherein: R₁ is selected from the group consisting of: naphthalene,anthracene, pyrene, fluorene, fluorenone and oligophenylene, R₂ is(OCH₂CH₂)_(m)CH₃ where m=0-1000, R₃ is selected from the groupconsisting of: H, OH, alkyloxide, alkanol, ethyleneoxide, carbonate andtrialkylamine, a+b+c=1 wherein 0<a<1, 0<b<1, and 0<c<1, and n=1-10million.
 2. A method for making an electrode for use in a lithium ionbattery comprising the steps of: a) forming a solution of a solvent anda conductive polymer of the formula

wherein: R₁ is selected from the group consisting of: naphthalene,anthracene, pyrene, fluorene, fluorenone and oligophenylene, R₂ is(OCH₂CH₂)_(m)CH₃ where m=0-1000, R₃ is selected from the groupconsisting of: H, OH, alkyloxide, alkanol, ethyleneoxide, carbonate andtrialkylamine, a+b+c=1 wherein 0<a<1, 0<b<1, and 0<c<1, and n=1-10million; b) to this solution adding micro or nanoparticles of at least 1element selected from the group consisting of: silicon, Sn, and graphiteto form a slurry; c) mixing the slurry to form a homogenous mixture; d)depositing a thin film of said thus obtained mixture over top of asubstrate; e) drying the resulting composite to form said siliconelectrode.
 3. A lithium ion battery having a silicon electrodeincorporating a conductive polymer binder having repeating units of theformula:

wherein: R₁ is selected from the group consisting of: naphthalene,anthracene, pyrene, fluorene, fluorenone and oligophenylene, R₂ is(OCH₂CH₂)_(m)CH₃ where m=0-1000, R₃ is selected from the groupconsisting of: H, OH, alkyloxide, alkanol, ethyleneoxide, carbonate andtrialkylamine, a+b+c=1 wherein 0<a<1, 0<b<1, and 0<c<1, and n=1-10million.